1. Field of the Invention
The present invention relates to a core structure of an integral heat-exchanger in which corrugate fins of a first heat-exchanger and those of a second heat-exchanger are integral with one another.
2. Description of Related Art
A core structure of an integral heat-exchanger is shown in Laid-open Japanese Patent Application (Tokkai-hei) 10-9783. For clarifying the present invention, the core structure of the publication will be briefly described with reference to FIGS. 6, 7 and 8 of the accompanying drawings.
As is seen from FIG. 6 which shows a sectional view of a part of the integral heat-exchanger, the core structure 100 generally comprises first parallel flat tubes 1 (only two are shown), second parallel flat tubes 2 (only two are shown) which are positioned behind the first tubes 1 and a plurality of corrugated fins 3 (only one is shown) each of which comprises a front part 3a interposed at upper and lower folded edge portions thereof between paired two of the first tubes 1, a rear part 3b interposed at upper and lower folded edge portions thereof between paired two of the second tubes 2 and a center part 3c through which the front and rear parts 3a and 3b are integrally connected. When in use, the core structure 100 is arranged so that the first tubes 1 are in front of the second tubes 2 with respect to a direction of air flow that is produced when an associated motor vehicle runs. (For ease of description, such air flow will be called “running air flow” in the following description.) That is, the first tubes 1 are those through which a refrigerant running in a cooling system of an automotive air conditioner flows to be cooled and the second tubes 2 are those through which an engine cooling water from a water jacket of an associated engine flows to be cooled. Usually, the second tubes 2 are much heated as compared with the first tubes 1.
The front and rear parts 3a and 3b of the corrugated fins 3 are each formed with plurality of louvers 3a′ and 3b′ for improving heat radiation effect of the core structure 100.
As is seen from FIGS. 6 and 7, the center part 3c of the corrugated fins is formed with parallel louvers 3e. Each louver 3e comprises a fully raised elongate flat portion 3h which is parallel with a major flat portion of the center part 3c. Due to provision of the parallel louvers 3e, a heat transfer between the first and second tubes 1 and 2, particularly the heat transfer from the highly heated second tubes 2 toward the less heated first tubes 1 is obstructed.
However, hitherto, producing the corrugated fins 3 with such parallel louvers 3e has needed a skilled and thus expensive punching technique because of the following reasons.
That is, as is seen from FIGS. 7 and 8, the parallel louvers 3e are produced by punching a corresponding part (viz., center part 3c) of the corrugated fin 3. With this punching, the corresponding part is cut and partially raised up to produce bridge-like louvers 3e each including the elongate flat portion 3h and two rectangular supporting portions 3i. Due to the nature of the punching, upon punching, portions which are to be formed into the rectangular supporting portions 3i are considerably expanded. Thus, if the supporting portions 3i are positioned extremely close to folded edge portions 3j of the corrugated fin 3 that are also considerably expanded, cracks 3k tend to appear at the bent portions 3j as is seen from FIG. 8. Thus, hitherto, it has been difficult to provide the parallel louvers 3e with a sufficient length “L1”. Of course, a satisfied heat transfer obstruction is not expected when the parallel louvers 3e fail to have a sufficient length “L1”.